The human eye can suffer a number of maladies causing mild deterioration to complete loss of vision. While contact lenses and eyeglasses can compensate for some ailments, ophthalmic surgery is required for others. Generally, ophthalmic surgery is classified into posterior segment procedures, such as vitreoretinal surgery, and anterior segment procedures, such as cataract surgery. More recently, combined anterior and posterior segment procedures have been developed.
The surgical instrumentation used for ophthalmic surgery can be specialized for anterior segment procedures or posterior segment procedures or support both. In any case, the surgical instrumentation often requires the use of associated consumables such as surgical cassettes, fluid bags, tubing, hand piece tips and other consumables.
A surgical cassette can provide a variety of functions depending on the procedure and surgical instrumentation. For example, surgical cassettes for cataract surgeries (e.g., phacoemulsification procedures) help manage irrigation and aspiration flows into and out of a surgical site. Surgical cassettes can also provide support for fluid bags, a manifold for directing vacuum/pressure to surgical instrumentation, and other functionality.
The fluid levels of an infusion/irrigation chamber and an aspiration chamber of a surgical cassette are measured to determine the amount of remaining fluid for procedure and fluid flow characteristics. To accurately determine the level of fluid in a chamber, the system employing the cassette should be calibrated to determine when the cassette is empty. Therefore, a method of zeroing a cassette chamber is needed.